(1) Field of the Invention
The present invention relates to a high-powered semiconductor laser array apparatus used for optical recording, optical communications, making a hole, welding and the like. The present invention also relates to a manufacturing method for such a semiconductor laser array apparatus, and to a multi-wavelength laser emitting apparatus using such semiconductor laser array apparatuses.
(2) Description of the Related Art
Recently, high-power semiconductor lasers are required for optical recording, optical communications, making an hole, and welding.
In order to meet such a requirement, there is a well-known semiconductor laser apparatus in which a plurality of laser oscillation units are formed in an array structure on the same substrate.
In this apparatus, a high-power light output is obtained by condensing a plurality of laser beams emitted from a plurality of laser oscillation units provided on the same substrate into a spot. Note that in this specification, a laser oscillation unit refers to a portion emitting laser beams and a portion guiding the laser beams.
However, laser beams emitted from those laser oscillation units are different from each other in the wavelength and phase. Therefore, when these laser beams are condensed into a spot, they interfere with each other. As a result, a high-power laser output according to the number of laser oscillation units cannot be obtained.
To cope with the problem, Japanese Laid-Open Patent Application No. H5-226765 discloses a semiconductor laser apparatus. In this apparatus, a plurality of laser oscillation units are placed close to each other on the same substrate so that laser beams from the laser oscillation units interfere with each other at the region of a current blocking layer where laser beams are leaked, whereby the wavelengths and phases of the laser beams can be matched with each other. The laser beams emitted from laser oscillation units are focused into one spot, whereby a high-power semiconductor laser apparatus can be realized.
Meanwhile, when a plurality of array structures are combined, much higher light output power can be expected as compared with only one array structure. However, in the above-stated apparatus, laser beams emitted from the laser oscillation units in the same array structure can be matched with each other in wavelength and phase, but laser oscillation units across different array structures cannot be matched.
Next, some laser emitting apparatuses are applicable for industrial uses such as welding and punching. In these apparatuses, a higher optical power is required. Therefore, gas lasers (such as CO2 lasers and excimer lasers), and solid-state lasers (such as YAG lasers) are currently dominant in this field.
However, a laser emitting apparatus using a gas laser or a solid-state laser inevitably increases in size owing to the structural limitations. Particularly, a laser emitting apparatus using a gas laser needs a gas container within them. Hence, even if a target to be machined is small, an apparatus has to be in a large-scale structure. As a result, a large space is necessary for installing the apparatus, and an expensive apparatus cost is inevitable. In addition, since luminous efficiencies of the gas lasers and solid-state lasers are bad, the apparatus consumes a large amount of electric power. Moreover, in case of gas lasers, their maintenance cost is increased for refilling the gas.
Meanwhile, various workpieces have been developed in accordance with developments of materials. Especially, in case that a workpiece fabricated by mixing two kinds of materials whose laser absorption coefficients are different from each other is processed by the above-stated laser emitting apparatuses, the following problems occur.
The wavelength of laser beam emitted from the above-stated apparatus is fixed at a specific single wavelength, so the wavelength is difficult to be changed. For instance, assuming the workpiece is made of materials A and B, and the material A has a high absorption coefficient for a laser beam with a wavelength xcex1, while the material B has a low absorption coefficient for the laser beam, then the laser power has to be increased in order to melt the material B as well. As a result, the temperature of the material A excessively increases, which causes inappropriate parts to be melted. Consequently, in case of making a hole in the above workpiece with these laser apparatuses, a diameter of the hole is larger than the intended dimension and the machining precision deteriorates greatly.
In the above case, it is preferable to also use a laser beam with a wavelength xcex2. However, it is difficult to change the wavelength of the laser beam in the gas or solid-state multi-wavelength laser emitting apparatus as stated above.
Also in various other fields, there is a demand for a small-sized and high-power laser application equipment with multi-wavelength.
The first object of the present invention is to provide a semiconductor laser array apparatus in which the above-stated plurality of array structures are combined so that laser beams emitted from the plurality of array structures are matched in wavelength and phase (hereafter called xe2x80x9cphase lockingxe2x80x9d), and a manufacturing method for the same.
The second object of the present invention is to provide a multi-wavelength laser emitting apparatus that realizes a small-sized but relatively high-power laser appliance which emits various laser beams having different wavelengths.
The first object is achieved by a semiconductor laser array apparatus made up of: a first laser array structure which includes, a plurality of first laser oscillation units which are arranged side by side at an interval, and a first current blocking material which fills a space between each pair of adjacent first laser oscillation units; and, a second laser array structure which includes, a plurality of second laser oscillation units which are arranged side by side at an interval, and a second current blocking material which fills a space between each pair of adjacent second laser oscillation units, wherein, when the semiconductor laser array apparatus is activated, laser beams generated by the first laser array structure and the second laser array structure leak to the outside of the first and second laser array structures so as to form first and second distribution regions of the laser beams, and the first and second laser array structures are closely disposed so that the first and second distribution regions contact or overlap with each other.
This construction enables phase locking between the first and second laser array structures. Consequently, in case of condensing laser beams emitted from the laser array structures into one spot, a high light output power can be obtained.
The above construction may include a construction in which a semiconductor layer is formed between the first and second laser array structures, a thickness of the semiconductor layer is adjusted so that the first and second distribution regions contact or overlap with each other.
The above constructions may also include a construction in which an optical waveguide layer which is interposed between the first and second laser array structures, and introduces laser beams oscillated by each of the first and second laser oscillation units, wherein the first and second distribution regions contact or overlap with each other within the optical waveguide layer. The optical waveguide layer is made of a material whose refractive index is larger than that of the clad layer or the like but smaller than that of the active layer. Here, the refractive indexes can be easily controlled by appropriately adjusting a composition of semiconductor materials (the amount of Al or the like).
Here, in the above constructions, at least adjacent two laser oscillation units among the first laser oscillation units are optically coupled with each other, and at least adjacent two laser oscillation units among the second laser oscillation units are optically coupled with each other.
Here, in the above constructions, the first and second current blocking materials fill the spaces so as to form a plurality of first and second stripes, respectively, the optical coupling in the first laser oscillation units is conducted by means of coupling waveguides, each coupling waveguide is formed by removing a part of each of the first stripes in a stripe groove shape, and the optical coupling in the second laser oscillation units is conducted by means of coupling waveguides, each coupling waveguide is formed by removing a part of each of the second stripes in a stripe groove shape.
Here, in the above constructions, the optical coupling of the first laser oscillation units is conducted by allowing adjacent laser oscillation units to merge with each other, and the optical coupling of the second laser oscillation units is conducted by allowing adjacent laser oscillation units to merge with each other.
Here, in the above constructions, the first laser oscillation units has a plurality of first stripe-shaped patterns which are extended from one end facet of the apparatus and a plurality of second stripe-shaped patterns which are extended from the other end, the first and second stripe-shaped patterns are alternately arranged along the vertical direction to their longitudinal direction, and the optical coupling of the first laser oscillation units is conducted between the first and second stripe-shaped patterns, the second laser oscillation units has a plurality of third stripe-shaped patterns which are extended from one end facet of the apparatus and a plurality of fourth stripe-shaped patterns which are extended from the other end, the third and fourth stripe-shaped patterns are alternately arranged along the vertical direction to their longitudinal direction, and the optical coupling of the second laser oscillation units is conducted between the third and fourth stripe-shaped patterns.
Here, in the above constructions, the optical coupling of the first laser oscillation units is conducted by allowing the first distribution regions to contact or overlap with each other, and the optical coupling of the second laser oscillation units is conducted by allowing the first distribution regions to contact or overlap with each other.
Here, the above constructions further include a first electrode which has a first polarity, and which sandwiches the first laser array structure and the second laser array structure; and a second electrode which has a second polarity opposite to the first polarity, and which is formed on both end portions of a top surface of a conductive layer located between the first laser array structure and the second laser array structure.
Here, the above constructions further include a window mirror structure which prevents heat generation and which is formed at end portions of the apparatus where the end portions of the first laser array structure and the second laser array structure face respectively.
This construction prevents the optical absorption at the end facets of the laser oscillation units, which prevents heat generation there.
Here, the above constructions further include an insulating unit which is formed at portions where an electric power is applied to the surface of the window mirror structure.
This construction further prevents heat generation.
Here, in the above constructions, forbidden bands of the first and second current blocking materials are wider than those of active layers in the first and second laser oscillation units respectively, and refractive-indexes of the first and second current blocking materials are smaller than those of the first and second laser oscillation units.
This construction enables a distribution region of laser beams to expand by reducing the optical absorption at the current blocking layer, whereby it becomes easy to optically couple adjacent optical oscillation units with each other.
The first object is also achieved by the manufacturing method for the semiconductor laser array apparatus made up of: a first step for forming the first laser array structure in which the plurality of first laser oscillation units are arranged side by side; and a second step for forming the second laser array structure in which the plurality of second laser oscillation units are arranged side by side so that a top surface of the second laser array structure faces a top surface of the first laser array structure, wherein, in the second step, the second laser array structure is formed on the first laser array structure according to an MOCVD method or an MBE method.
The first object is also achieved by the manufacturing method for the semiconductor laser array apparatus made up of: a first step for forming the first laser array structure in which the plurality of first laser oscillation units are arranged side by side; and, a second step for forming the second laser array structure in which the plurality of second laser oscillation units are arranged side by side so that a top surface of the second laser array structure faces a top surface of the first laser array structure, wherein, in the second step, after the optical waveguide layer is formed on the first laser array structure according to an MOCVD method or an MBE method, the second laser array structure is formed according to the same method.
The first object is also achieved by the manufacturing method for the semiconductor laser array apparatus made up of: a first step for forming the first laser array structure in which the plurality of first laser oscillation units are arranged side by side; a second step for forming the second laser array structure in which the plurality of second laser oscillation units are arranged side by side; and a third step for attaching the first laser array structure to the second array structure. (method A)
The first object is also achieved by the manufacturing method for the semiconductor laser array apparatus made up of: a first step for forming the first laser array structure in which the plurality of first laser oscillation units are arranged side by side; a second step for forming the second laser array structure in which the plurality of second laser oscillation units are arranged side by side; and a third step for attaching the first laser array structure to the second array structure, wherein, the third step follows a step for forming an optical waveguide layer on at least one surface of the first and second laser array structures (method B).
The first object is also achieved by the above manufacturing method A for the semiconductor laser array apparatus further including a fourth step for conducting hydrophilic treatment to at least one surface of surfaces of the first and second laser array structures, prior to the third step, wherein heat treatment is conducted in the presence of hydrogen in the third step.
The first object is also achieved by the above manufacturing method B for the semiconductor laser array apparatus further including a fourth step for conducting hydrophilic treatment to at least one surface among surfaces of the optical waveguide layer, and the first and second laser array structures, prior to the third step, wherein heat treatment is conducted in the presence of hydrogen in the third step.
The second object is achieved by a multi-wavelength laser emitting apparatus made up of: a plurality of semiconductor laser array apparatuses which emit laser beams of different wavelength from each other; and an optical element which condenses the plurality of laser beams into a predetermined position; wherein at least one semiconductor laser array apparatus includes a plurality of laser array structures, each of which includes a plurality of laser oscillation units arranged side by side at an interval and a current blocking material filling the interval between each pair of adjacent laser oscillation units, and at least two adjacent laser array structures, among the plurality of laser array structures, are optically coupled with each other.
Here, it is preferable that the above multi-wavelength laser emitting apparatus further includes an adjusting means which adjusts a position where laser beams are condensed by shifting the optical element; a laser driving means which selects a laser array structure which emits laser beams of a designated wavelength and activates the selected laser array structure; and a control means which controls the adjusting means in accordance with the designated wavelength.
The above-stated semiconductor laser array apparatuses may be applied to this multi-wavelength laser emitting apparatus.